The inventive subject matter generally relates to closures for closing openings in, or making connections between, objects or parts thereof. The closures are magnetically based and are intended to be suitable for use as replacements for zippers and other such closures. For example, the inventive closures are suitable for use in apparel and other textile-based objects, and footwear applications.
A magnet attracts ferromagnetic materials and magnets attract magnets when opposite poles are aligned. Magnetic fields may be permanent or selectable. That is, a magnetic field may be selectively established in an object by an electric current or induced in certain materials such as smart fluids that may be magnetized when in the presence of an applied magnetic field.
All moving charged particles, such as electrical current, produce magnetic fields. Current conducted in a wire creates magnetic field lines in concentric circles around the length of the wire. Current conducted in two adjacent wires generate magnetic fields that create magnetic forces that can attract the wires together or repel the wires, depending on the relative directions of the currents.
A class of fluids (referred to herein as “smart” fluids) has properties that can be varied when subjected to external electromagnetic forces. Examples include magnetorheological (MR) fluids that change rheological behavior in response to an applied magnetic field; ferrofluids that become strongly magnetized in the presence of a magnetic field; and electrorheological (ER) fluids that respond to an electric field with a change in the fluid's viscosity.
MR fluids are suspensions of micrometer-sized, magnetically polarizable particles in oil or other liquids. When an MR fluid is exposed to a magnetic field, the normally randomly oriented particles within the fluid form chains of particles in the direction of the magnetic field lines. This alignment increases the apparent viscosity of the fluid and there is magnetization along the chains of aligned particles. MR elastomers are suspensions of micrometer-sized, magnetically polarizable particles in a thermoset elastic polymer or rubber. The stiffness of the elastomer structure may be changed by varying the strength of the applied magnetic field. MR fluids and elastomers typically change viscosity when exposed to a magnetic field in as little as a few milliseconds. Discontinuing the exposure of the MR fluid or elastomer to the magnetic field reverses the process: the fluid loses magnetism and returns to a lower viscosity state, and the elastomer returns to its lower modulus state. MR fluids enclosed in structural elements have been disclosed in U.S. Pat. No. 5,547,049.
Ferrofluid is a stable suspension of magnetic particles in a liquid carrier. The particles, which typically have an average size of about 10 nm, are coated with a surfactant that prevents the particles from agglomerating, even when a strong magnetic field is applied. A wide variety of magnetic solids, surfactants, and carriers are known and available and can be used to tailor ferrofluid properties to intended applications.
Regardless of their composition, ferrofluids generally behave the same. In the absence of a magnetic field, the magnetic moments of the particles in the ferrofluid are randomly distributed, and the fluid has no net magnetization. When a magnetic field is applied to a ferrofluid, the magnetic moments of the particles orient along the field lines and the ferrofluid becomes magnetized. Ferrofluids typically respond almost immediately to changes in the applied magnetic field and when the applied field is removed, the moments quickly randomize again. The retention force of a ferrofluid can be adjusted by changing either the composition of the fluid or the magnetic field that induces magnetization.
Electrorheological (ER) fluids are dispersions that can rapidly and reversibly vary their apparent viscosity in the presence of an applied electric field. ER fluids are dispersions of finely divided solids (<50 microns) in hydrophobic, electrically non-conducting oils that have the ability to change their rheological characteristics, even to the point of becoming solid, when subjected to a sufficiently strong electrical field. When the field is removed, the fluids revert to their normal liquid state. The current passing through the ER fluid may be extremely low and still achieve the desired state change.
“Printed electronics” refers to printing methods that create electrical devices on various substrates. Common printing equipment and processes, such as screen-printing, flexography, gravure, offset lithography, and inkjet, may be suitable for defining electrical patterns on material. Electrically functional electronic inks are deposited on the substrate creating active or passive devices such as conductors, transistors, and resistors.
A class of textiles that may include electronic circuitry is e-textiles or smart fabrics in which digital components are embedded. E-textiles include textiles with classic electronic devices such as conductors, integrated circuits, LEDs, and batteries embedded into garments and textiles with electronics integrated directly into the textile substrates. This may include passive electronics such as conductors and resistors or active components like transistors, diodes, and solar cells.
Another field in which conductors and circuits may by integrated into textiles is “fibertronics” that uses conducting and semi-conducting materials in the fabrication of a woven material. Commercial fibers such as metallic fibers can be woven or sewn as part of a garment or other textile item. Organic electronics may be suitable because they can be conducting, semiconducting, and designed as inks and plastics.
Advancements in this field are ongoing and future textiles with electromagnetic properties may be suitable for use in implementing the inventive concepts disclosed herein.
Closures couple things together and as used herein refer to apparatuses that connect one object to another object, or one portion of an object to another portion of the same object. Known examples of releasable closures include zippers, buttons, Velcro, laces, latches, magnets, and snaps. Examples of non-releasable closures, that is, closures that are intended to be long-term, include nails, screws, and most adhesives.
Releasable closures are common in clothing, footwear, camping gear such as tents, sleeping bags, and backpacks, athletic gear such as pads, helmets, and safety gear, upholstered items such as seats and couches, and a multitude of other applications in all fields of endeavor. Considerations in selecting a releasable closure for an application include its weight, resistance to abuse, resistance to environmental factors (water, dust, wind, etc.), retention strength, flexibility, aesthetics, ease of use, profile (e.g., thinness), and reliability.
Magnetic closure systems are known that are based on zipper-like, interdigitating magnetic elements. U.S. Pat. No. 6,983,517 entitled “Releasable Closure System” discloses the use of an MR fluid in the heads of interdigitating elements. Heads on an interdigitating element may include an MR fluid that can be magnetically switched on or off to change their configuration so that they engage complementary heads on an opposing interdigitating element.
Unfortunately, significant disadvantages exist for closure systems that are based on interdigitating elements. Such systems require slide closures, complicating fabrication and use. Interdigitating elements are also prone to failure. The entire closure fails if a single element fails. They are also difficult or expensive to engineer for weather resistance as each element is point of entry for moisture or air because seals are imperfect in conventional designs.
Accordingly, the art of releasable closures can benefit from a releasable closure that includes properties not found in prior art devices and that provides reliability, ease of use, resistance to environmental factors, and good retention strength.
There is also a need for garment assemblies that more securely and aesthetically couple together. And there is a need for easy to operate means for coupling garments and other objects and to open or close common openings for such objects.
The inventive subject matter disclosed herein, in its various possible embodiments and applications, addresses the foregoing and other needs and overcomes disadvantages in the prior art.